In response, the armies in Egypt and Judaea declared Vespasian emperor on July 1.[1]p43 In his bid for imperial power, Vespasian joined forces with Mucianus, the governor of Syria, and Primus, a general in Pannonia. Primus and Mucianus led the Flavian forces against Vitellius, while Vespasian gained control of Egypt. On 20 December, Vitellius was defeated, and the following day Vespasian was declared emperor by the Roman Senate.

Little factual information survives about Vespasian's government during the ten years he was emperor. His reign is best known for financial reforms, the successful campaign against Judaea, and several ambitious construction projects such as the Colosseum. Upon his death in 79, he was succeeded by his eldest son Titus.